The deformation of Okun's law over the business cycle.

Summary This thesis highlights the asymmetric aspect of the output elasticity of unemployment in the United States and in Europe. The first part of this empirical work returns to an estimate of the "true" value of the Okun coefficient corrected for publication bias. We use a meta-analysis and show that an important aspect of the distortion of the coefficient lies in the choice of the endogenous variable. In the second chapter, we show that Okun's law implies in its foundations a procyclical behavior of productivity generated by the practice of labor retention. The US economy shows a significant deformation of the Okun coefficient during recessions and recoveries since the mid-1980s, when productivity lost its procyclical character. In Germany and France, on the other hand, the Okun coefficient deforms little over the cycle. This European specificity could be due to the nature of macroeconomic fluctuations. Thus, the German economy experiences macroeconomic shocks with a strong transitory and persistent character. Nevertheless, the rest of the European countries have shocks of a permanent nature. In the last chapter, we show that real GDP and unemployment can share an asymmetric cointegration relationship that seems to be associated with an asymmetric Phillips curve.